The invention concerns a method and apparatus for removing an improperly inserted weft thread from an air-jet loom, wherein the individual wefts or picks are inserted by means of a main jet nozzle and auxiliary jet nozzles into a shed formed by warp threads, whereupon the wefts are beaten-up into the fell of the fabric and then cut from the supply of weft thread kept ready in the vicinity of the main jet nozzle. The weft thread insertion is monitored by a weft monitor mounted on the opposite side of the shed from the main jet nozzle. If the weft thread is defectively inserted into the shed and is not sensed by the weft monitor at the shed exit, the cutting of the defectively inserted weft is prevented and a program comprising a series of steps for error correction is initiated.
According to the program, the loom is either stopped in or stopped and moved to a position maintaining the shed with the improperly inserted weft thread. Thereafter a predetermined length of weft thread from a ready supply is introduced into the shed and is advanced together with the improperly inserted weft thread to the side of the shed opposite the main jet nozzle, after which the newly inserted length of weft thread is severed from the weft thread of the ready supply and, together with the improperly inserted weft thread, is removed from the shed on the side opposite the main jet nozzle.
In a known device and procedure of this kind (European Patent Publication No. 0 207 470), a predetermined length of weft thread about twice the normal length, i.e., the width of the fabric, is taken from the ready supply of weft thread and hangs adjacent the defectively inserted weft thread prior to its being blown into the shed. The predetermined length of weft thread is blown through the shed and arrives in the area of a catch means located on the side of the shed opposite the main jet nozzle. By means of the tensile force exerted by the catch means on the newly inserted length of weft and the defectively inserted weft thread, the defectively inserted weft thread is expected to be peeled off the fell of the fabric, with the tensile force applied to the defectively inserted weft thread being essentially transverse to the direction of the warp yarns.
It is also known (German Patent Publication No. DT 22 28 131) to reverse the loom in the event of a defectively inserted weft thread to a position where the auxiliary jet nozzles are activated and constantly blow out air because of the operative position to which the batten of the loom has been reversed. An ejector means then seizes the free end of the defectively inserted weft thread while it is still connected to the ready supply of weft thread and moves the end into the vicinity of the auxiliary jet nozzles. During this time the ready supply of weft thread is clamped to prevent additional weft thread from being taken from the supply by the ejector means moving the defectively inserted weft thread. Thereafter the defective weft thread is blown by the auxiliary jet nozzles and removed from the fell of the fabric. The clamp holding the ready supply of weft thread is released and newly inserted weft thread is blown together with the defectively inserted weft thread to the side of the fabric opposite the main jet nozzle where, following cutting, it is removed from the shed.